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Aggressive histological subtypes of thyroid cancer are rare and have a poor prognosis. The most important aggressive subtypes of thyroid cancer are Hürthle cell carcinoma (HCTC) and anaplastic and poorly differentiated carcinoma (ATC and PDTC). The American Thyroid Association recently published guidelines for the management of patients with ATC, but no specific guidelines have been done about HCTC. We performed an overview of the literature about the role of Fluorine-18-Fluorodeoxyglucose positron emission tomography or positron emission tomography/computed tomography (FDG-PET or PET/CT) in aggressive histological subtypes of thyroid cancer. Only few original studies about the role of FDG-PET or PET/CT in HCTC, PDTC, and ATC have been published in the literature. FDG-PET or PET/CT seems to be useful in staging or followup of invasive and metastatic HCTC. FDG-PET or PET/CT should be used in patients with ATC in initial staging and in the followup after surgery to evaluate metastatic disease. Some authors suggest the use of FDG-PET/CT in staging of PDTC, but more studies are needed to define the diagnostic use of FDG-PET/CT in this setting. Limited experience suggests the usefulness of FDG-PET or PET/CT in patients with more aggressive histological subtypes of DTC. However, DTC presenting as radioiodine refractory and FDG-PET positive should be considered aggressive tumours with poor prognosis.

Patients with autonomously functioning thyroid nodules (AFTN) may not have an abnormal TSH value, particularly in iodine-deficient areas.To verify the accuracy of TSH as screening test in detecting AFTN and to evaluate ultrasonographic features of thyroid nodules which have resulted autonomously functioning at thyroid scintigraphy (TS).Seventy-eight patients with nodular goiter, no marker of autoimmunity and at least one AFTN at TS were selected and divided in: Group 1 (no.=25) with TSH0.35 IU/l, and Group 2 (no.=53) with TSH≤0.35 IU/l.In Group1 the mean nodule diameter was 19.8±9.4 mm; 12 nodules were isoechoic, 2 hyperechoic, and 11 hypoechoic. Vascular pattern was type I in 4, type II in 6 and type III in 15 nodules. In Group 2 the mean nodule diameter was 28.6±14.2 mm; 27 nodules were isoechoic, 9 hyperechoic and 17 hypoechoic. Vascular pattern was type I in 14, type II in 15 and type III in 24 nodules.In our study TSH alone was not able to identify AFTN in 32% of the patients. All hot nodules predominantly showed an isoechoic pattern with peri-intranodular vascularization; however, the presence of this pattern was not statistically significant. Moreover, we noticed a weak inverse correlation between the diameter of AFTN and TSH level. In conclusion, TS is the most sensitive tool to detect AFTN, allowing a precocious diagnosis even in the presence of a normal TSH value.